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Model output discussion - after the beast, what next?


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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    4 minutes ago, bluearmy said:

    To me, the eps spreads don’t take the cold pool n of the midlands. The odd outlier may go to the border but outliers should be excluded. Eps say the envelope is Birmingham to Brussels. That puts Kent in the middle. Clearly other models are elsewhere. 

     

     

    Agreed, but on some sites or different interpretations, that would skew the spread, I think the people mentioning the borders are just hopecasting, Kent a good starting point from now on IMO, I would narrow it down for the heaviest snow showers to the South Midlands southwards. still wouldn't rule out seeing falling snow in my location but a few fakes in the wind is a whole different ball game to a few days ago when disruptive snow was a distinct possibility as far North as Durham.

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    The UKMO 144 has teased me out if hibernation - for a comment. 144 shows a very meridional flow across 50N with deep cold filtering into Scandi- could be a sharp transition from mild to cold

    No mate, I'm still in winter mode as long as the Gfs shows potential arctic blasts..hope it continues!❄❄❄❄❄

    Ahhh another chocolate teapot in your post... I believe the last one froze. It seems that we are seeing the second response to the SSW with another surge of negative zonal mean u winds heading fo

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    Posted
  • Location: East Ham, London
  • Location: East Ham, London

    Plenty of cold air on the GFS 06Z OP and while fans of snow look to be disappointed (except in Kent and parts of the SE), fans of cold have plenty to look forward to.

    Hopefully (and here's me hope-casting now), some crisp dry days and some sharp night time frosts.

    Close to an ice day on Sunday for many:

    102-580UK.GIF?14-6

    Not extraordinary but certainly unusual.

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    Posted
  • Location: West Sussex
  • Weather Preferences: Extreme cold & snow
  • Location: West Sussex
    1 hour ago, Summer Sun said:

    Nice update from UKMO extended at t168 showing milder air starting to move in from the west

    ukm2.2018032100_168_lant.troplant_prp_fcst.gentracker.thumb.png.262687fd6dad00107e18e9e78f8d3234.png

     

    ECM taking a similar route only difference is a bit more rain for Scotland

    ecm2.2018032100_168_lant.troplant_prp_fcst.gentracker.thumb.png.9db74a9cd594dd128ff292deb277a7bb.png

    :)

    True - and shockingly mild throughout most of the UK according to GFS 06z

    image.thumb.png.19d16a7b690756716f2d455128f801e6.png

    :laugh:

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    Posted
  • Location: Erith. SE London/kent 40m asl
  • Weather Preferences: Winter Snow, extreme weather, mainly sunny mild summers though.
  • Location: Erith. SE London/kent 40m asl

    Good news, latest FAX chart has moved everything slightly further north again.:wink:

    T84/00z today

    T96/12z yesterday

    fax84s.gif

    fax96s.gif

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    Posted
  • Location: bingley,west yorks.81 absl
  • Location: bingley,west yorks.81 absl
    12 minutes ago, snowray said:

    Good news, latest FAX chart has moved everything slightly further north again.:wink:

    T84/00z today

    T96/12z yesterday

    fax84s.gif

    fax96s.gif

    Shows a nice trough Saturday for most from the east.

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    Posted
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast
  • Weather Preferences: Severe Storms and Snow
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast
    1 minute ago, IPredictASnowStorm said:

    Its going to be dry and cold according to the GFS

    Highest risk in this cold situation for snowfall is still looking towards East Anglia and South East, South East more especially so. But models are still playing with things moving it north or south! Dry depends on where you are 

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    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
    56 minutes ago, Purga said:

    True - and shockingly mild throughout most of the UK according to GFS 06z

    image.thumb.png.19d16a7b690756716f2d455128f801e6.png

    :laugh:

    What do you expect at 6am in March?!

    A more sensible time shows double digits quite widely

    ukmaxtemp.thumb.png.4de3decc4d1b5950191b38a932166ca6.png

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
    1 hour ago, feb1991blizzard said:

    Agreed, but on some sites or different interpretations, that would skew the spread, I think the people mentioning the borders are just hopecasting, Kent a good starting point from now on IMO, I would narrow it down for the heaviest snow showers to the South Midlands southwards. still wouldn't rule out seeing falling snow in my location but a few fakes in the wind is a whole different ball game to a few days ago when disruptive snow was a distinct possibility as far North as Durham.

    I've taken another look at the ECM ensembles for where the cold pool hits. Below is roughly where the centre of the cool pool goes through. Most of them are well developed enough to affect areas 100-200 miles either side of this (so for instance, most cold pools centred on southern England will probably be big enough to affect N England, and cold pools going through N France will be big enough take in SE England).

    Scotland: 2 ECM ensemble members

    North England (Nottingham + northwards): 4

    South England (Birmingham + southwards): 25

    North France: 15

    S France / not really developed: 5

    So yes I do agree with you Feb and yes my very quick post earlier was a bit too general - the idea of the cold pool hitting Glasgow is right at the extreme of the options and is probably only a 10% chance, whereas affecting the English Channel is perhaps 80%. 

    However ... while I now agree a Scotland event would be a surprised, a significant snowfall event for NE England cannot yet be ruled out IMO. When I look at historical charts, NE England has often received lots of snowfall on the coast when on the edge of a cold pool and uppers are below minus 12C. Both these things still in play. But equally, to be clear, it is south of the Humber which remains the area of most interest for now.

    And just to add a bit more using the clusters ... if I lived in N England and looked at cluster 1 (by far the biggest), I certainly would not count myself out of the game if I lived in N England:

    ec-ens_nat_z500scenarios_2018031400_096.

    Edited by Man With Beard
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    Posted
  • Location: Birmingham (Solihull), West Midlands
  • Weather Preferences: Sunshine, thunder, hail & heavy snow
  • Location: Birmingham (Solihull), West Midlands

    In some ways agree with Nick regarding the possible inaccuracy of convection forecasts.

    The models had this problem of forecasting convective activity with the Easterly we had at the beginning of the month where some seemed to under-estimate how widespread convective snow showers would be. A few of them had a fair chunk of the West Midlands dry, and yet pretty much the whole region saw snow showers (with maybe just the odd spot missing out)

    Edited by DiagonalRedLine
    Changing some bits
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    Posted
  • Location: West Sussex
  • Weather Preferences: Extreme cold & snow
  • Location: West Sussex
    12 minutes ago, Summer Sun said:

    What do you expect at 6am in March?!

    A more sensible time shows double digits quite widely

    ukmaxtemp.thumb.png.4de3decc4d1b5950191b38a932166ca6.png

    Actually not about 5C below normal lowest temps in the morning SS...:D

    Across the UK, March temperatures average a daily high of 10 degrees Celsius (50 degrees Fahrenheit) and a low of 3 °C (37 °F).

    Southern England

    Average March temperatures
    High °F Low °F Place High °C Low °C
    50 37 Birmingham 10 3
    51 38 Cambridge 11 3
    50 40 Eastbourne 10 5
    52 41 Exeter 11 5
    50 37 Ipswich 10 3
    53 39 London 11 4
    49 38 Lowestoft 10 4
    50 41 Newquay 10 5
    52 39 Oxford 11 4
    46 36 Princetown, Dartmoor Park 8 2

    Northern England

    Average daily temperatures in March
    High °F Low °F Place High °C Low °C
    49 38 Blackpool 9 3
    50 38 Grimsby 10 3
    44 33 Malham Tarn, Yorkshire Dales 7 1
    50 38 Manchester 10 3
    49 36 Newcastle 10 2
    48 36 Penrith 9 2
    50 38 Sheffield 10 3
    Edited by Purga
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    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

    06z JMA brings the -12 850's in around the SE corner with -8 850's stretching up to around Northumberland

    J84-21.thumb.GIF.74006b0d637e21190d7fc6094d8f49ec.GIFJ84-7.thumb.GIF.4a292bbf6f69d8af1e9f6ef5b9efbdb8.GIFJ84-594.thumb.GIF.9af453c5f4fadccc481a7ef94e8639c9.GIF

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    Posted
  • Location: Cheltenham, Gloucs.
  • Location: Cheltenham, Gloucs.
    5 minutes ago, Georgie said:

    So the West country will be left out if we do get snow? just trying to read between the lines

    The most reliable models tend to be looked at for clear reference to placement of weather systems before they arrive. We are, for example, waiting for high pressure to evolve around Scandinavia. Once we can see some of the model's prior guidance coming to fruition, I'd say we follow the rest of that model's guidance for a while. There is a more mathematical way of looking at possible evolutions and that is to look at all the models at the same of day (or near as the same as we need the data to be similar), we can compare them or a group of runs alongside each other, forming an ensemble. The ensembles offer an average and that is sometimes eye opening. 

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    Posted
  • Location: st albans
  • Location: st albans
    25 minutes ago, nick sussex said:

    Not sure how many times this has been said before but convection forecasts on any model are useless.

    The only thing they are better as is frontal precip.

    Yet still there’s loads of drama in here over forecasts which have been been proven to be a waste of space in the past.

     

    Ec precip predictions were pretty good on convergance troughs from 5/6 days out. The more convective stuff was a struggle but even then it didn’t do too badly. It’s not a micro tool hour by hour which is pretty much what you need to assess convective precip. 

     

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    Posted
  • Location: Cottingham
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Cottingham

    image.thumb.png.abc8c02765fd90f8409c7340d637acbb.png

    Swingometer updated again for 06z's.

    Still an unclear pciture. I think the 00z saw a massive swing because a fair few of the runs are right on the border of what I would class as a direct or indirect hit from the cold pool lol.

    The 06z ensembles seem to be firming up on a gradual tranition to milder weather through the week, however whether some places will see good falls of snow is still unclear.

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    Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

    I'm looking forward to the high pressure shown on the Gfs 6z which should bring plenty of strengthening late march sunshine to most of the uk.???

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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE
    17 minutes ago, bluearmy said:

    Ec precip predictions were pretty good on convergance troughs from 5/6 days out. The more convective stuff was a struggle but even then it didn’t do too badly. It’s not a micro tool hour by hour which is pretty much what you need to assess convective precip. 

     

    Troughs are a different matter. I’ve yet to see a forecast for normal convection that was accurate.

    Anyway until there’s agreement on the depth of cold and available instability then we’re really none the wiser.

    By the way for members who like these precip forecasts the WRF has now gone from almost zip precip to three distinct streamers for Sunday at 6 am.

    One near the Wash into the north Midlands , one Essex into ne London and one east Kent into the Channel Islands.

     

    Edited by nick sussex
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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
    6 minutes ago, nick sussex said:

    Troughs are a different matter. I’ve yet to see a forecast for normal convection that was accurate.

    Anyway until there’s agreement on the depth of cold and available instability then we’re really none the wiser.

    By the way for members who like these precip forecasts the WRF has now gone from almost zip precip to three distinct streamers for Sunday at 6 am.

    One near the Wash into the north Midlands , one Essex into ne London and one east Kent into the Channel Islands.

     

    HIRLAM definitely the best last time in my opinion - slightly overdid it but overall was closer to the mark than the models that underdid it. Should be within range by Friday morning.

    Edited by Man With Beard
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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE
    Just now, Man With Beard said:

    HIRLAM definitely the best last time in my opinion - slightly overdid it but overall was closer to the mark than the models that underdid it. Should be within range by tomorrow lunchtime.

    Yes apparently that did well with the last easterly .

    The WRF 0.1 which I alluded to in my post is another of the huge amount of higher resolution models we now have access to.

    Things have certainly changed in recent years with just how many models we have at our disposal.

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    Posted
  • Location: Stunning Shropshire
  • Weather Preferences: Snow!
  • Location: Stunning Shropshire
    29 minutes ago, nick sussex said:

     

    Things have certainly changed in recent years with just how many models we have at our disposal.

    Yes.......too many, for some! :nea:

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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    The latest Met Office early warning mentions a possible convergence zone around the Wash and the Thames estuary .

    And with the chance these snow showers could spread west.

    So strength of the flow quite important here, also what happens to low pressure over Southern Europe as that impacts both the flow and instability available into the UK.

     

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    Posted
  • Location: st albans
  • Location: st albans
    5 minutes ago, nick sussex said:

    The latest Met Office early warning mentions a possible convergence zone around the Wash and the Thames estuary .

    And with the chance these snow showers could spread west.

    So strength of the flow quite important here, also what happens to low pressure over Southern Europe as that impacts both the flow and instability available into the UK.

     

    and will affect the direction of those isobars - slight changes will change where any streamers affect.

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